The objective of the proposed work is to provide evidence on the question of the sequence of events ensuing between the uptake of steroid by the target tissue and its response in terms of increased synthesis of enzymes and other proteins. We will investigate the mechanisms by which steroid sex hormones can bring about increased synthesis of RNA in their target tissues, the mechanisms by which these RNAs mediate the enzymatic and metabolic responses of the tissue, and the nature of the types of RNA involved. We have set up a cell-free system from wheat germ embryos which carries out the transition of the poly (A) rich RNA isolated from uteri. Using RNA produced in deciduomata of rat uteri, we will compare the effects of estrogen injection into castrate rats bearing deciduomata comparing these to rats not receiving estrogen. We will also continue our analysis of our finding that the injection of FSH into the testes of intact male rats increased the synthesis of poly (A) rich RNA. We found that FSH is effective in stimulating RNA synthesis in the cells of the seminiferous tubules whereas LH stimulates messenger RNA synthesis in the interstitial cells. Cyclic AMP stimulates messenger RNA synthesis in both types of cells. We are carrying out a kinetic analysis of these responses to the gonadotropic hormones. BIBLIOGRAPHIC REFERENCES: Villee, C.A. and Buchi, K.: A Micromethod for Measuring the Activation of Estradiol Receptors of the Rat Uterus. J. of Steroid Biochemistry 6, 1467-1769, 1975. Keichline, L. Darwin, Villee, Claude A. and Wassarman, Paul M.: Structure of Eukaryotic Chromatin: Evaluation of Periodicity Using Endogenous and Exogenous Nucleases. Biochimica et Biophysica Acta 425, 84-94, 1976.